Query from database with variable

Hi All,

I'm trying to use the variable i created and assigned in query database SQL query. 
But it seems the studio can't detect the variable. 
Appreciate if anyone could guide on how to use variable in this case?
Variable type simple short text.

"SELECT * FROM table
WHERE field1 = variable"

Thank you.
Sean

Answer:
"SELECT * FROM table
WHERE field1 =" + variable